Influence of chemistry on the flux-gradient relationships for the NO-O3-NO2 system

It is shown that K-theory has to be modified for chemical systems that react with time scales similar to the turbulence time scale. In such systems, the value of the exchange coefficient depends not only on the turbulence parameters, but also on the chemical reaction rates. As an example, the NO-O₃-NO₂ chemical system is studied. Using second-moment equations, new flux-gradient relationships for the neutral atmospheric surface layer are obtained which depend on the time scale ratios of turbulence ( _t ) and chemical reactions ( _ch), i.e., reactive K-theory. Within the framework of this reactive K-theory, the flux of a chemical species is both a function of the concentration gradients of the three chemical species involved and of the ratio of the time scale of turbulence to the time scale of chemistry. In the special case of slow chemistry ( _{t ch}) inert K-theory is applicable.The reactive exchange coefficients are implemented in a surface-layer model that calculates the flux and concentration profiles of the three chemical species. The results of the calculations of the effective exchange coefficients are different for reactive K-theory and inert K-theory; the differences are largest for nitric oxide, but smaller for ozone and nitrogen dioxide.